Many hydraulic jack and air piston devices for lifting are known commercially and in the prior art. The below-listed Patents are typical of these devices. However, they have shortcomings for certain purposes.
In farm and commercial use, often there is available a tractor with hydraulic cylinders and a source of hydraulic energy and power. In such farm and commercial use, there are quite often heavy lifting problems, including, for example, the tractor itself if one of its large tires should blow out. In such case, it may cost $30 or more for a farmer to hire an appropriate professional to come to his farm, jack up the tractor, remove the wheel and take it for repair. Alternatively, if he can remove the tire and get it into town, the cost for repair of the tire is far less.
There exists now a definite need for a heavy duty, dependable jack useable in such circumstances and to lift other heavy objects, such as houses, grain bins and the like, for leveling. In such heavy duty use, it is eminently desirable, indeed necessary, that the jack construction be such that no part of the jack will twist with respect to another part or rotate under heavy load conditions. Yet further, a particular problem lies in the fact that all conventional hydraulic cylinders (or air pistons) have a limited throw with respect to their own size. In order to have the greatest versatility in a heavy duty jack, then, means must be provided to permit the maximum feasible throw of the load carrying sleeve with respect to the supporting post (the male-female elements of the jack), independent of limitations of the throw of the hydraulic cylinder or air piston. In such case, it is necessary to provide means for securing the movable part of the jack with respect to the stationary part whenever adjustments with respect to engagement with the hydraulic cylinder or air piston are made. These considerations lie as the basis for the development of the subject improved heavy duty tractor and implement jack.